Changes of venous blood flow velocity waveforms in fetuses with supraventricular tachycardia

Studies in the fetal lamb have shown that atrial pacing beyond a rate of 300-320 beats/min may be associated with dramatic changes of venous blood velocity waveforms, an increase of venous pressure by up to 75%, hydrops, polyhydramnios and placental edema. The aim of our study was to determine the 'critical' heart rate frequency in the human fetus. In 11 fetuses (five with and six without hydrops) with supraventricular tachycardia, pulsed wave Doppler analysis of flow velocity waveforms of the inferior vena cava, the ductus venosus and the left hepatic vein were performed before and after drug treatment. In ten cases cardioversion was achieved by in utero antiarrhythmic drug therapy; in one case treated with digoxin and flecainide the supraventricular tachycardia was decreased to 160-190 beats/min with disappearance of hydrops. Before intrauterine treatment of supraventricular tachycardia, pulsatile reversal of blood flow in the inferior vena cava, ductus venosus and left hepatic vein was visible, with monophasic forward flow during systole and reversed flow during diastole in ten of 11 fetuses. One fetus with supraventricular tachycardia of 195 beats/min showed a normal biphasic forward flow pattern. During drug-induced sinus rhythm, a normal biphasic forward venous blood flow pattern was shown in all ten cases. In five cases pulsatile reversal was demonstrated during a drug-induced reduction of the heart rate from 280 to 210 beats/min and a normal biphasic forward flow velocity waveform appeared during supraventricular tachycardia below 210 beats/min.(ABSTRACT TRUNCATED AT 250 WORDS)     

Improved results of liver transplantation in patients with portal vein thrombosis

OBJECTIVE: To analyze the impact of preexisting portal vein thrombosis (PVT) on the operative management and outcome of liver transplantation. DESIGN: Retrospective review of 1423 patients who received transplants over 11 years. SETTING: Tertiary referral center. PATIENTS OR OTHER PARTICIPANTS: Seventy patients who underwent liver transplantation who had preexisting PVT. INTERVENTIONS: Portal vein thromboendovenectomy, vein grafting, or use of portal collateral veins for inflow during liver transplantation. MAIN OUTCOME MEASURES: Postoperative PVT, intraoperative transfusion, retransplantation rate, 30-day and 1-year actuarial survival rates. RESULTS: Operative management consisted of thromboendovenectomy in 61 cases, vein graft to the superior mesenteric vein in 6 cases, and vein graft to other mesenteric veins in 3 cases. The incidence of posttransplant PVT was 3% (n = 2). The mean +/- SD transfusion requirement was 23 +/- 18 U. The 1-year actuarial survival rate was 74% but improved from 66% in the first 35 cases to 82% in the latter 35 cases. CONCLUSIONS: Thromboendovenectomy is the procedure of choice for PVT. Results of liver transplantation in patients with PVT improve significantly with experience gained and are equivalent to results in patients without PVT.     

Transvenous hemodynamic assessment of experimental arteriovenous malformations. Doppler guidewire monitoring of embolotherapy in a swine model

BACKGROUND AND PURPOSE: A Doppler guidewire was used to monitor progressive changes in draining vein flow parameters during experimental embolotherapy in a swine arteriovenous malformation (AVM) model. METHODS: A microcatheter was positioned superselectively in the main arterial feeder and main draining vein in each of 10 AVM models in swine. With use of the Doppler guidewire, preembolization arterial and venous average peak velocities (APVs) and pulsatility indices were recorded. The device was left in the draining vein during transarterial particulate (in 8 swine) or liquid adhesive (in 2 swine) embolization, and continuous transvenous flow during and after treatment was monitored. Periembolization Doppler flow parameters were correlated qualitatively with angiographic changes in the nidus. RESULTS: Preembolization draining vein flow was pulsatile, with a mean APV of 38.9 +/- 13.7 cm/s. After embolization, this changed significantly to a less pulsatile or nonpulsatile pattern, with a lower mean APV of 9.2 +/- 4.9 cm/s (P = .0001). A novel expression, the maximum minus the minimum peak velocity (MxPV-MnPV), was used in evaluating the transvenous Doppler spectra. This was reduced significantly after embolization from a mean of 11.1 +/- 3.5 cm/s to 6.7 +/- 2.5 cm/s (P = .0025). Objective periembolization hemodynamic changes were detected in the draining veins earlier than the visually subjective angiographic changes within the nidus. CONCLUSIONS: Transvenous Doppler guidewire assessment of two parameters, APV and MxPV-MnPV, is useful in the hemodynamic evaluation of experimental arteriovenous shunting and may be used for future objective and quantitative monitoring during endovascular AVM embolotherapy.     

Abnormal fetal aortic velocity waveform and minor neurological dysfunction at 7 years of age

Measurements of fetal aortic blood flow velocity and fetal growth were performed in 178 pregnancies. In 87 cases, the estimated fetal weight was > or = 2 SD below the gestational age-related mean of the population. Three fetuses died in utero. In 149 children (85%), a neurological examination was performed at 7 years of age with special emphasis on minor neurological dysfunction. The frequency of the more severe form of minor neurological dysfunction, MND-2, was higher in the group with blood flow class (BFC) III (absent or reversed end-diastolic flow velocity (8/21) than in the group with BFC 0 (normal velocity waveform) (14/105). Logistic regression analysis revealed that abnormal blood flow class, both independently and in combination with other factors, was the most significant predictor of MND-2. The association found between abnormal fetal aortic velocity waveforms and adverse outcome in terms of minor neurological dysfunction suggests that hemodynamic evaluation of the fetus has a predictive value regarding postnatal neurological development.     

Blood transfusion and lung function in chronically anemic patients with severe chronic obstructive pulmonary disease

OBJECTIVE: To study in anemic patients with chronic obstructive pulmonary disease (COPD) whether blood transfusion reduces minute ventilation and work of breathing (WOB). DESIGN: We prospectively evaluated the minute ventilation and WOB in 20 anemic adults (hemoglobin of <11 g/dL). Ten patients had severe COPD and ten patients were without lung disease. Measurements were made before and after receiving red blood cell transfusion; post-transfusion measurements were made 24 to 36 hrs after the last transfusion. SETTING: The study was performed in the intensive care unit of a tertiary referral center for home mechanical ventilation and for patients considered difficult to wean from mechanical ventilation. PATIENTS: Twenty clinically stable patients (12 female, eight male) with chronic anemia were studied. Ten patients with COPD (mean forced expiratory volume in 1 sec: 0.55+/-0.1 [SD] L) were compared with ten patients without lung disease. All participants had adequate renal and left ventricular function. INTERVENTIONS: Patients received 1 unit of packed red blood cells for each g/dL that their hemoglobin value was less than an arbitrarily defined target value of 11.0 to 12.0 g/dL. Each unit was transfused over 2 hrs and < or =3 units in total was given. MEASUREMENTS AND MAIN RESULTS: Esophageal pressure was measured from a catheter which was positioned in the middle of the esophagus. Flow was measured using a pneumotachygraph connected to a mouthpiece while a nose clip closed the nostrils during the measurements. From these data, respiratory rate, minute ventilation, and inspiratory resistive WOB were computed. Arterial blood gas values, oxygen saturation, hemoglobin, and hematocrit were also measured, and oxygen content was calculated before and 24 to 36 hrs after transfusion. In patients with COPD, hemoglobin increased from 9.8+/-0.8 to 12.3+/-1.1 g/dL due to a mean transfusion of 2.2+/-0.4 (SD) units of red blood cells. There was a reduction in the mean minute ventilation from 9.9+/-1.0 to 8.2+/-1.2 L/min (p < .0001); correspondingly, WOB decreased from 1.03+/-0.24 to 0.85+/-0.21 WOB/L (p< .0001). The capillary P(CO2) increased from 38.1+/-6.0 to 40.7+/-6.8 torr (5.1+/-0.8 to 5.8+/-0.9 kPa) (p < .05). Similarly, capillary P(O2) changed from 56.9+/-8.9 to 52.8+/-7.0 torr (7.6+/-1.2 to 7.0+/-0.9 kPa) (p < .05). In anemic patients without lung disease, minute ventilation, WOB, and the capillary blood gas values did not change after increase of the hemoglobin by a similar degree. CONCLUSIONS: We conclude that red blood cell transfusion in anemic patients with COPD leads to a significant reduction of both the minute ventilation and the WOB. In these patients, transfusion may be associated with unloading of the respiratory muscles, but it may also result in mild hypoventilation.     

Flow parameters of the normal arterial duct in the fetus

The increasing interest in arterial duct flow patterns in the fetus warrants the establishment of an accurate range of normal flow parameters throughout gestation. We therefore undertook a prospective echocardiographic study of 181 normal fetuses from the 16th to the 40th week of gestation. Adequate Doppler interrogation of the duct was obtained in 71% of the fetuses examined. Peak gradient, mean gradient and flow velocity integral in systole and diastole were digitized. The peak systolic gradient throughout pregnancy measured 2.7 +/- 1.4 mmHg with a slight tendency to increase with gestational age (r = 0.58). The peak ratio, defined as peak systolic gradient divided by peak diastolic gradient (28.1 +/- 14.9), did not vary significantly with gestational age. This time-independent index complements peak systolic flow in the assessment of normal and abnormal ductal flow. The definition of the normal range for ductal flow parameters, based on this relatively large fetal population, should facilitate the accurate diagnosis of fetal duct constriction.     

Doppler echocardiographic assessment of fetal blood flow redistribution during maternal hyperoxygenation

In a retrospective analysis of the standard protocols for fetal echocardiographic examination, 27 fetuses (mean gestational age 29 +/- 5.4 weeks) with ascites were evaluated. Fetal cardiomegaly (increased heart area/chest area ratio), the presence or absence of atrioventricular valve regurgitation, inferior vena cava and ductus venosus Doppler flow velocity and umbilical vein pulsation were evaluated quantitatively in a group of survivors and non-survivors. A statistically significant difference between the two groups was found for the presence of atrioventricular valve regurgitation (p = 0.003), and for cardiomegaly (p = 0.009). There was no statistical difference for the presence of abnormal venous flow and umbilical pulsation (p > 0.05). Abnormal venous Doppler flow velocities in the inferior vena cava and ductus venosus were observed more frequently than umbilical vein pulsation. The mean heart area/chest area ratios in the group of survivors and in the group of non-survivors were 0.34 +/- 0.09 and 0.48 +/- 0.08, respectively (p < 0.001). The mean gestational ages at the time of diagnosis of ascites in the groups of survivors and non-survivors were 33 +/- 3.3 weeks and 28 +/- 5.1 weeks, respectively (p < 0.05); the mean gestational ages at the time of delivery were 35.6 +/- 2.3 weeks and 33.3 +/- 4.9 weeks, respectively (p = 0.33). In terms of different echocardiographic features as well as the gestational age of the unborn patient with ascites, there is apparently no single indicator of a poor prognosis. Our results suggest that the prognosis is usually poor in a fetus with ascites, when cardiomegaly is detected, as well as the presence of tricuspid and mitral valve regurgitation. This is regardless of the type of venous flow and regardless of the etiology of the ascites.     

Portal hemodynamics after large-volume paracentesis in patients with liver cirrhosis and tense ascites

Large-volume paracentesis with a plasma expander has been extensively evaluated and shown to be an effective and safe therapy. While hepatic and systemic hemodynamics have been studied extensively, there is little information on portal hemodynamics by duplex Doppler. Portal vein diameter, portal flow velocity, and portal blood flow were measured with duplex Doppler in 11 cirrhotic patients before and 24 hr after large volume paracentesis. There were no significant changes in the portal vein diameter (9.88+/-2.62 mm vs 10.09+/-2.73 mm), portal flow velocity (10.65+/-2.60 vs 10.01+/-2.58 cm/sec), and portal blood flow (488+/-288.9 vs 502+/-73.38 ml/min), before and 24 hr after large-volume paracentesis. Thus, significant changes in portal hemodynamics do not occur after large-volume paracentesis.     

Fusion variations of pancreatic ducts in patients with anomalous arrangement of pancreaticobiliary ductal system

Portal vein flow was recorded by color Doppler sonography in 31 patients with chronic heart failure and 18 control subjects. Compared with patients showing a forward flow (Group A), those with reversed portal vein flow (Group B) had higher prevalence of tricuspid regurgitation (75% vs. 43%), hepatic congestion (100% vs. 30%) and ascites (50% vs. 18%), and showed higher right atrial pressure (25.3 +/- 3.01 mmHg vs. 11.8 +/- 5.75 mmHg, p < 0.01). In controls, portal vein pulsatility ratio was 0.66 +/- 0.08, in Group A it was 0.46 +/- 0.28 (p < 0.01), in Group B -0.60 +/- 0.19 (p < 0.01). Portal vein pulsatility ratio negatively correlated with right atrial pressure (r = -0.87; p < 0.01). In Group A, hepatic congestion, ascites and tricuspid regurgitation were associated with a higher portal vein pulsatility. This study indicates that portal vein pulsatility ratio reflects the level of impairment of the right heart.     

Combined effect of weak permanent and variable magnetic fields, adjusted to the cyclotron resonance of amino acid ions, on development of Ehrlich ascites carcinoma in mice

OBJECTIVE: The authors studied the changes in retinal blood flow (RBF) and oxygen reactivity in a major temporal vein in patients with central retinal vein occlusion (CRVO). PARTICIPANTS: Eleven patients with nonischemic CRVO approximately 7 weeks from onset of disease. INTERVENTION: Laser Doppler velocimetric measurement of RBF and vessel reactivity to inhaling 60% oxygen. Measurements were performed at baseline and 3 months. RESULTS: Flow velocity in the affected eye had increased significantly by 3 months, from 1.6 +/- 0.4 cm/second to 2.0 +/- 0.4 cm/second (P = 0.02). Retinal blood flow, however, remained unchanged (13.7 +/- 5.8 microl/minute versus 15.0 +/- 6.5 microl/minute). The two comparable RBF values, despite differing velocity values, suggest that the relatively normal baseline value was achieved through higher intravascular pressure at baseline (Bernoulli's principle). This is supported by the fact that oxygen reactivity had improved from 2.1% +/- 3.6% at baseline to 3.8% +/- 3.1% (P = 0.001) at 3 months, which suggests an improved ability to respond to hyperoxia from reduced intravascular pressure. CONCLUSION: Intravascular pressure in CRVO appears to continue to decrease during the first 5 months after the onset of CRVO, indicating continuing reduction in the degree of outflow obstruction during this time.     

Anti-GBM glomerulonephritis in mice lacking nitric oxide synthase type 2

To determine the relationship between quantitative Doppler parameters of portal, hepatic, and splanchnic circulation and hepatic venous pressure gradient (HVPG), variceal size, and Child-Pugh class in patients with alcoholic cirrhosis, we studied forty patients with proved alcoholic cirrhosis who underwent Doppler ultrasonography, hepatic vein catheterization, and esophagoscopy. The following Doppler parameters were recorded: time-averaged mean blood velocity, volume flow of the main portal vein flow, and resistance index (RI) of the hepatic and of the superior mesenteric artery. Doppler findings were compared with HVPG, presence and size of esophageal varices, and Child-Pugh class. There was a significant inverse correlation between portal velocity and HVPG (r = -.69), as well as between portal vein flow and HVPG (r = -.58). No correlation was found between RI in the hepatic artery or superior mesenteric artery and HVPG. No correlation was found between portal vein measurements and presence and size of varices. Severe liver failure was associated with lower portal velocity and flow. In patients with alcoholic cirrhosis, only portal vein blood velocity and flow, but neither hepatic nor mesenteric artery RI, are correlated to the severity of portal hypertension and to the severity of liver failure.     

Superior mesenteric artery blood flow velocimetry: cross-sectional Doppler sonographic study in normal fetuses

Our objectives were to describe the flow velocity waveform of the fetal superior mesenteric artery and to establish a nomogram for its pulsatility index. In a cross-sectional study using color Doppler ultrasonography, superior mesenteric artery flow velocimetry was investigated prospectively in 96 healthy fetuses of between 14 and 37 weeks of gestation. In normal fetuses the pulsatility index measurements showed a slight but insignificant increase over the course of gestation (r = 0.26; P > 0.5). The lowest mean +/- standard deviation for pulsatility index in the superior mesenteric artery was 1.86 +/- 0.45 (95% confidence interval 1.67-2.06), recorded between 18 and 21 weeks' gestation. Thereafter the pulsatility index increased to 1.94 +/- 6.4 (95% confidence interval 1.74-2.8) at 22 to 25 weeks, and from weeks 26 to 29 it increased to 2.18 +/- 0.52 (95% confidence interval 1.91-2.46). During the third trimester and at term, the mean pulsatility index of 2.23 +/- 0.32 (95% confidence interval 1.43-3.03) did not change significantly with gestational age. In normal fetuses, except for the early stages, a relatively stable vascular resistance of the intestinal circulation was found. The application of this nomogram in clinical practice may facilitate evaluation of intestinal perfusion in compromised fetuses with blood flow centralization.     

The importance of accurate lesion placement in posteroventral pallidotomy. Report of two cases

OBJECTIVES: The effects of anemia of prematurity during bronchopulmonary dysplasia (BPD) as well as on the metabolic and erythropoietic functions were determined before and after a transfusion. Fourteen anemic (Hb range: 65-88 gm/L), oxygen dependent (fraction of inspired oxygen < or = 35%), nonventilated, preterm infants with BPD were studied at a postnatal age of 6 +/- 2 weeks. STUDY DESIGN: Cardiac output, heart rate, mean velocity of circumferential fiber shortening, shortening fraction (SF), and stroke volume were assessed by pulsed and continuous wave Doppler echocardiography. Values for resting oxygen consumption, carbon dioxide production, and energy expenditure were obtained by indirect calorimetry. The affinity of oxygenated hemoglobin was determined by a blood oxygen dissociation analyzer. RESULTS: An increased hemoglobin level resulted in a suppression of erythropoietin secretion (p < 0.001), whereas heart rate, cardiac output, stroke volume, and SF decreased (p < 0.05). Weight gain before and after transfusion were similar. Plasma lactate levels decreased from 1.6 +/- 0.3 to 1.2 +/- 0.3. Oxygen consumption, carbon dioxide production, and energy expenditure were not affected. CONCLUSIONS: Anemia of prematurity and BPD increase heart rate, cardiac output, stroke volume, and SF. These hemodynamic compensatory responses are normalized by transfusion.     

Cardiotocogram compared to Doppler investigation of the fetal circulation in the premature growth-retarded fetus: longitudinal observations

It was our objective to compare computerized fetal heart rate analysis with blood flow velocity waveform analysis of the arterial and venous fetal circulation in intrauterine growth retardation. We report five illustrative cases with longitudinal observations of fetal Doppler findings and fetal heart rate between 23 and 32 weeks of gestation. Blood flow waveforms were recorded from the umbilical artery, middle cerebral artery, descending aorta, ductus venosus and inferior vena cava. Fetal heart rate was analyzed by a computer system according to the Dawes-Redman criteria. The time sequence of deterioration is described individually for each fetus. An abrupt increase in pulsatility of ductus venosus waveforms with loss of forward flow velocity during atrial contraction preceded abnormally low short-term variation of fetal heart rate. With advanced gestational age and concomitant maternal disease, we observed severe alterations of flow velocity waveforms within 12 h of normal Doppler measurements, which is in contrast to findings in the second trimester, in which severely abnormal venous waveforms were observed over a period of several weeks before intrauterine death occurred. In a fetus with terminally low short-term variation, normal venous waveforms indicated fetal well-being despite an abnormal cardiotocogram (CTG). We challenge the current concept that the CTG is the best available parameter to determine the optimal time for elective delivery of premature growth-retarded fetuses. Deterioration in ductus venosus blood flow seems to precede an abnormal CTG and thus heralds the need for delivery.     

Pharmacodynamics of intracavernously injected drugs and cavernous wall resistance

The volumetric flow rates, mean and pulsatile, in the aorta and its major branches were measured in nonfed, anesthetized rabbits, using a transit time Doppler ultrasonic flowmeter. Anesthesia was maintained with isoflurane, and a vasodilator was applied topically during the measurements to avoid introducing additional flow resistance due to vasoconstriction. The cranial mesenteric and celiac arteries received the bulk of the aortic flow, (mean +/- SD) 29.5 +/- 6.6% and 23.3 +/- 5.8%, respectively, for mean flow. The brachiocephalic artery received as much as 14.7 +/- 3.2%, while each of the other branches received a considerably smaller fraction: 7.1 +/- 2.5% for the left subclavian artery, 6.2 +/- 2.6% and 5.1 +/- 2.2%, respectively, for the right and left renal arteries, and 6.0 +/- 2.5% for each of the two iliac arteries. Flow divisions were nearly the same in paired vessels. Peak pulsatile flow divisions were similar to their steady flow counterparts in the brachiocephalic, left subclavian, celiac, and cranial mesenteric arteries, but were smaller in the renal and iliac arteries, although the difference was not statistically significant. Reverse flow from one or more of the branches back into the aorta occurred in diastole in seven of eight rabbits studied.     

Spanish study of quality of life in migraine (I). Profile of the patient with migraine attending neurology clinics

This study reports our experience with 67 intrauterine transfusions (IUTs) carried out for 27 cases of severe Rh alloimmunization, which could be useful to other developing countries with similar situations. Most of the mothers were from sections of India other than Mumbai, their socioeconomic status was low, and they were referred during the second or third trimester. The mean gestation age at first IUT was 27+/-2.9 weeks and maternal anti-D titer ranged from 1:32 to 1:512. Ultrasonography (USG) was normal in eight cases, but showed minimal or gross ascites in 8 and 11 cases, respectively. The mean +/- SD hematocrit (HCT) in three groups defined by USG was 23.5+/-1.7, 15.9+/-4, and 12+/-5.9, respectively. Amniotic fluid analysis, which proved to be an important investigation, indicated IUT in eight cases having normal USG. Six cases were severely anemic (Hb deficit >7 g/dl). By fetal cell staining, the percentage of the donor's red cells in the fetal circulation was determined. Besides Hb, blood group, direct antiglobulin test, and mean cell volume, this parameter was also useful in assessing efficacy of IUT and the need for an exchange transfusion after birth. Of 11 fetuses having gross ascites, eight and one each from the remaining two groups, were stillborn. One death may be procedure related. Two neonates died due to hemorrhagic disorder and prematurity. The overall survival rate was 55.6%. Late referral, severe Rh alloimmunization, volume overload, delay in IUT because of nonavailability of blood and use of nonirradiated blood could be the reasons for the poor outcome. Strategies for improving results are discussed.     

Sex and crime: heterotrimeric G proteins in fungal mating and pathogenesis

The coronary circulation is the major determinant of myocardial oxygen balance which in turn is necessary for adequate cardiac function under a variety of conditions. Experiments in the fetal lamb suggest short-term functional coronary autoregulation in response to increase in afterload and acute hypoxemia. Long-term, acute-on-chronic hypoxemia is associated with a marked increase of maximal myocardial flow reserve suggesting coronary vascular angio-neogenesis during the period of chronic hypoxemia. In the human fetus, flow velocity waveforms from the coronary arteries may be obtained by color-coded and pulsed wave Doppler sonography in normally developed fetuses from 31 weeks of gestation onwards under favorable imaging conditions. Coronary blood flow may also be visualized in selected fetuses with intrauterine growth restriction, absent or reversed end-diastolic flow in the umbilical artery, cephalization of blood flow and abnormal flow patterns in the precordial veins and the umbilical vein. In these fetuses visualization of coronary blood flow may be possible as early as 26 weeks gestation and is consistently associated with a significant increase in the peak velocity index for veins in the ductus venosus. In this circulatory state, visualization of coronary blood flow is suddenly very easy. This "visualization threshold" may be a sign of maximal increase in coronary blood flow in an attempt to "spare" the fetal heart of hypoxemia. Although highly operator dependent, demonstration of coronary blood flow in intrauterine growth restriction identifies fetuses at high risk for intrauterine fetal death and postpartum circulatory failure.     

MR measurement of time-dependent blood pressure variations

An MR imaging method for measuring intravascular pressure variations is introduced. The technique is based on estimates of vascular compliance and vessel distension, which are obtained from a correlation of spatial and temporal velocity derivatives and measurements of the velocity gradient in the direction of flow, respectively. The accuracy of the technique was determined in vitro through a comparison of MR and transducer pressure measurements obtained in distensible vessel phantoms undergoing pulsatile flow. Results indicated that a root-mean-square error of 4-12% can be expected in phantoms covering a physiological range of compliance. In vivo feasibility was demonstrated by thoracic aorta pressure measurements, which produced pressure waveforms with an expected shape and magnitude.     

Disruption of p53 function in immortalized human cells does not affect survival or apoptosis after taxol or vincristine treatment

OBJECTIVE: We assessed the feasibility of contrast-enhanced color Doppler, power Doppler, and spectral duplex sonography for visualization and quantification of flow through transjugular intrahepatic portosystemic shunts (TIPS) in patients in whom the baseline sonographic evaluation was unsatisfactory. SUBJECTS AND METHODS: Thirty-three patients underwent color Doppler, power Doppler, and spectral duplex sonography after TIPS insertion or before TIPS revision (mean time interval +/- SD, 1 +/- 1 day). All sonograms were obtained before and after patients received echo-enhancing contrast material. Sonography was evaluated with regard to presence or absence of flow in the mid portion, portal segment, and hepatic segment of the shunt. The maximal peak velocity was measured in the mid portion of the shunt. For identifying and quantifying stenoses, the percentage of luminal diameter reduction was calculated at the tightest part of the shunt. Shunt angiography and measurements of portosystemic pressure gradients were independently evaluated and compared with the sonographic findings. RESULTS: Flow visualization on unenhanced color Doppler sonography was significantly improved through the use of power Doppler sonography and contrast-enhanced color Doppler and power Doppler sonography (p < .01). Between contrast-enhanced power Doppler and contrast-enhanced color Doppler sonography, a significant difference was found in the portal and hepatic segments (p < .05). All shunt stenoses (n = 8) and occlusions (n = 3) were revealed by power Doppler sonography, whereas color Doppler sonography failed to reveal six of eight stenoses. Compared with unenhanced sonography, the quality of spectral duplex sonography was improved in eight patients after contrast enhancement (p < .05). Maximal peak velocity ranged from 54 to 252 cm/sec (mean +/- SD, 132.7 +/- 52.1 cm/sec) in normal shunts and from 24.5 to 70.0 cm/sec (mean +/- SD, 45.0 +/- 18.9 cm/sec) in stenosed shunts. No correlation was found between maximal peak velocity and portosystemic pressure gradients (r = .28). CONCLUSION: Unenhanced power Doppler and contrast-enhanced color and power Doppler sonography can be helpful in the assessment of TIPS status in patients who previously underwent unsatisfactory sonography. These techniques may allow anatomic evaluation and quantification of shunt stenosis in most patients. Contrast enhancement may also considerably improve the quality of spectral duplex sonography.     

Insulin kinetics after portal and peripheral injection of [125I] insulin: II. Experiments in the intact dog

Insulin metabolism in man is usually investigated by peripheral injection of the hormone, whereas native insulin undergoes hepatic extraction prior to mixing in the general circulation. To quantify this difference, in 10 dogs [125I] insulin was injected into a peripheral vein, and the initial distribution volume (IDV), the metabolic clearance rate (MCR), and the mean transit time (t) were computed from the plasma disappearance curve of the immunoprecipitable activity. The splenic vein was then cannulated under pentobarbital anesthesia, and the parameters were again computed from the peripheral activity after portal introduction of the tracer. The MCR after portal injection [15.1 +/- (SE) 1.1 ml/min per kg] was greater (P is less than 0.001) than the MCR after peripheral administration (13.4 +/- 0.9 ml/min per kg). Also, IDV was larger (P is less than 0.01) after portal injection (167 +/- 12 vs. 138 +/- 10 ml/kg). Mean transit times did not change significantly. Insulin secretion rate (0.29 +/-0.04 mU/min per kg) and body insulin mass (7.03 +/- 1.5 mU/kg) were also measured. An estimate of hepatic extraction was obtained from the difference between the clearance rate values calculated following portal and peripheral injection. Under our experimental conditions, hepatic retention of insulin was found to be 19.6% (range 9.6-36.2%). The method is recommended for investigations in man.